- CHAPEL HILL - Core samples
from a deep-sea drilling expedition in the western Pacific clearly show
multiple episodes of warming that date back as far as 135 million years,
according to one of the project,s lead scientists. Analysis of the samples
indicates warming events on Earth were more common than researchers
previously
believed.
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- The expedition aboard the scientific drill ship
"JOIDES
Resolution," which ended in late October, also revealed that vast
areas of the Pacific Ocean were low in oxygen for periods of up to a
million
years each, said Dr. Timothy Bralower. A marine geologist, Bralower is
professor and chair of geological sciences at the University of North
Carolina
at Chapel Hill.
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- "These ocean-wide anoxic events were some of the
most radical environmental changes experienced by Earth in the last several
hundred million years," he said.
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- Along with Dr. Isabella Premoli-Silva, a
micropaleontologist
and stratigrapher at the University of Milan, Bralower served as co-chief
of the two-month expedition. Drilling took place on Shatsky Rise, an
underwater
plateau more than 1,000 miles east of Japan. Its purpose was to better
document and understand past global warming.
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- "In geologic time, episodes of warming began almost
instantaneously -- over a span of about a thousand years," Bralower
said.
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- "Warming bursts may have been triggered by large
volcanic eruptions or submarine landslides that released carbon dioxide
and methane, both greenhouse gases," he said.
"Besides reducing the ocean,s oxygen-carrying capacity, warming also
increased the water's corrosive characteristics and dissolved shells of
surface-dwelling organisms before they could settle to the bottom.
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- "In some especially striking layers of black,
carbon-rich
mud, only the remains of algae and bacteria were left," he
said.
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- "The sheer number of cores that reveal the critical
warming events found on this expedition -- three from the 125-million-year
event and 10 for the 55-million-year Paleocene event -- exceeds the number
of cores recovered for these time intervals by all previous ocean drilling
expeditions combined," Bralower said.
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- "This means that we will be able to reconstruct
in far better detail the nature of environmental changes that took place
back then than was previously possible," he said. "We'll also
have a better chance of determining the cause. Already we've seen signs
in the sediments for other undetected periods of warming, which suggests
that they were much more frequent than geologists have
thought."
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- Among periods of warmth likely caused by methane was
one occurring about 55 million years ago, the geologist said. Cores show
that 200,000-year-long event killed off 30 percent to 50 percent of deep
ocean life while stimulating evolution of new species near the
surface.
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- Twenty-seven scientists from seven countries and 62 crew
spent 35 days above Shatsky Rise on the expedition, which is expected to
boost understanding of current global warming, he said.
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- The Ocean Drilling Program is an international
partnership
of scientists and research institutions organized to study the evolution
and structure of the Earth. ODP is funded principally by the National
Science
Foundation, with contributions from its international partners.
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- A consortium of 16 U.S. academic institutions known as
the Joint Oceanographic Institutions manages the program. Texas A&M
University oversees science operations.
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- ___
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- Bralower can be reached at (919) 962-0704 or
bralower@email.unc.edu.
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- Photos showing life aboard the drill ship during the
expedition are available on the web at http://www-odp.tamu.edu/p
ublic/life/leg198.html.
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- News Services Contact:
David Williamson, (919) 962-8596
-
- University Of North Carolina
- News Services
- 210 Pittsboro Street, Campus Box 6210
- Chapel Hill, NC 27599-6210
- 919 962-2091
fax 919 962-2279
- www.unc.edu/news/newsserv
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